Ethylene regulates phosphorus remobilization and expression of a phosphate transporter (PhPT1) during petunia corolla senescence

Abstract

The programmed degradation of macromolecules during petal senescence allows the plant to remobilize nutrients from dying to developing tissues. Ethylene is involved in regulating the timing of nucleic acid degradation in petunia, but it is not clear if ethylene has a role in the remobilization of phosphorus during petal senescence. To investigate ethylene's role in nutrient remobilization, the P content of petals (collectively called the corolla) during early development and senescence was compared in ethylene-sensitive wild type Petunia×hybrida ‘Mitchell Diploid’ (MD) and transgenic petunias with reduced sensitivity to ethylene (35S::etr1-1). When compared to the total P content of corollas on the day of flower opening (the early non-senescing stage), P in MD corollas had decreased 74% by the late stage of senescence (advanced wilting). By contrast, P levels were only reduced by an average of 32% during etr1-1 corolla (lines 44568 and Z00-35-10) senescence. A high-affinity phosphate transporter, PhPT1 (PhPht1;1), was cloned from senescing petunia corollas by RT-PCR. PhPT1 expression was up-regulated during MD corolla senescence and a much smaller increase was detected during the senescence of etr1-1 petunia corollas. PhPT1 mRNA levels showed a rapid increase in detached corollas (treated at 1 d after flower opening) following treatment with low levels of ethylene (0.1 μl l-1). Transcripts accumulated in the presence of the protein synthesis inhibitor, cycloheximide, indicating that PhPT1 is a primary ethylene response gene. PhPT1 is a putative phosphate transporter that may function in Pi translocation during senescence.

From Model to Crop: Functional Analysis of a STAY-GREEN Gene in the Model Legume Medicago truncatula and Effective Use of the Gene for Alfalfa Improvement

“…5F). The most down-regulated are a phosphate transporter (Mtr.15323.1.S1_s_at) and a basic blue copper protein (Mtr.10725.1.S1_at), which may be involved in phosphate and copper salvage during senescence (Miller et al, 1999;Chapin and Jones, 2009). A putative ripening-related protein (Mtr.10361.1.S1_at) and a Cys proteinase (Mtr.43787.1.S1_at) have unchanged relative expression in NF2089 compared with the wild type (Fig.…”

Flower Senescence-Strategies and Some Associated Events

“…Most of the changes in gene expression are related to the remobilization of macromolecules and transport of the mobile compounds out of the petal. Degradation of macromolecules in the senescent cell is mainly due to autophagic processes in the vacuole; protein degradation in mitochondria, nuclei, cytoplasm; fatty acid breakdown in peroxisomes and nucleic acid degradation in nuclei (Bieleski, 1995;Mahagamasekera & David, 2001;Wagstaff et al, 2002;Jones et al, 2005;Narumi et al, 2006;Xu et al, 2006;Chapin & Jones, 2007;Hoeberichts et al, 2007;van Doorn & Woltering, 2008;Lerslerwong et al, 2009;Shibuya et al, 2009;Yamada et al, 2009).…”

“…It is the final event in the life of many plant tissues and is highly regulated process that involves structural, biochemical and molecular changes that in many cases bear the hallmarks of programmed cell death, PCD (Makrides & Goldthwaite, 1981;Noh & Amasino, 1999;Buchanan-wollaston & Morris, 2000;Rubinstein, 2000;Xu & Hanson, 2000;Mahagamasekera & David, 2001;Leverentz et al, 2002;Wagstaff et al, 2003;Jones et al, 2005;Rogers, 2006;Xu et al, 2006;Hoeberichts et al, 2007;Ichimura et al, 2009;Lerslerwong et al, 2009;Yamada et al, 2009). It is a dynamic and closely regulated developmental process which involves highly coordinated changes in gene expression and requires active gene transcription and protein translation (Hensel et al, 1993;Yamada et al, 2003;Hoeberichts et al, 2005;Jones, 2008;Chapin & Jones, 2007, 2009. It is largely an oxidative process involving a general degradation of cellular structures and the mobilization of the products of degradation to other parts of the plants or organs (Nichols & Ho, 1975;Feller & Keist, 1986;Bieleski, 1995;Fischer et al, 1998;van Doorn & Woltering, 2008).…”

Spatial and temporal distribution of mineral nutrients and sugars throughout the lifespan of Hibiscus rosa-sinensis L. flower

“…This may indicate that nitrogen is remobilized earlier than P in senescence program, according with the degradation of nucleic acids that is carried out at the latest stage of programmed cell death [29]. Moreover in corolla of transgenic petunia with reduced ethylene sensitivity, the reduction in P content occurred later than nitrogen [30], and recently Chapin and Jones [31] indicated an increase in phosphate transporters steady-state mRNA levels in corolla of senescing petunia that was correlated with a decrease in P content. In H. rosa-sinensis the decline in N and P content appeared to be more closely associated with accumulation of ABA -that peaked at opened flower stage and subsequently declined -rather than with the gradual increase in ethylene production that occurs throughout the flower development [32].…”